1. Field of the Invention
The present invention relates to a frequency control device applied to an RF signal processing system, such as an optical disk, and an information reproduction apparatus having the same.
2. Description of the Related Art
There is known a frequency detection device used as a clock oscillation frequency control for a phase locked loop (PLL) circuit and a rotation control for a spindle in an optical disk or a hard disk drive (HDD).
As the control for a clock oscillation frequency by the PLL, there is known the following two methods, for example.
A first method is that a frequency detection device, in which a reproduction signal is sampled with a reproduction clock generated by the PLL and a difference of a maximum length pattern of a sampled mark length/space length (hereinafter, referred to a T-length) with respect to a maximum T-length defined by a format is calculated to determine a frequency drift of a PLL clock, is used and a frequency control amount is fed back to the PLL.
A second method is that a frequency detection device, in which a frame sync pattern is detected and a difference of an interval between detected frame sync patterns with respect to an interval between frame sync patterns defined by a format is calculated to determine the frequency drift of a PLL clock, is used and a frequency control amount is fed back to the PLL (for example, referred to Japanese Unexamined Patent Application (Kokai) No. 11-149704).